Maki Zenin vs. Mai Zenin is a battle fought between sisters of the Zenin Family, Tokyo Jujutsu High second-year student Maki Zenin and Kyoto Jujutsu High second-year student Mai Zenin during the Spirit Bash Race competition of the 30th Annual Kyoto Sister-School Goodwill Event.
After eliminating Nobara by shooting her in the temple with a rubber bullet, Mai is suddenly confronted by her sister while hiding in the trees. Maki suggests her sister call for backup but Mai claims she wants Maki all to herself. She takes aim at her sister who asks for Mai to call her "big sis".
Mai loads her revolver to the replace the round she used against Nobara. While charging at her sister, Maki smiles as she recalls the first years talking about her. Irritated by Maki's smile, Mai fires her gun but Maki effortlessly slices the bullet in half. Then, Maki slices the branch acting as Mai's footing, dodging another bullet and kicks her opponent before she lands in one fluid instantaneous moment.
After Maki believes Mai to have fired all six bullets in her revolver, she charges forward to finish the fight. However, Mai's revolver is a faint and her cursed technique: Construction, which allows for her to create one more bullet at the cost of all her cursed energy.
Mai believes herself to have won, but Maki is able to catch the bullet barehanded. Although it burns her hand, Mai's last ditch effort failed against her opponent. Maki places her new sword at Mai's side, signifying her victory and her sister's elimination.
Mai is left to think about her relationship with Maki after and all throughout the fight. She desired to remain at home and discriminated on while Maki chose to go out at the expense of her sister. That resentment comes from a promise between them that Maki broke. So her sister considers her a liar and she hates her for it.